ExclamationTopology.java

/**
 * Licensed to the Apache Software Foundation (ASF) under one or more contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.  The ASF licenses this file to you under the Apache License, Version
 * 2.0 (the "License"); you may not use this file except in compliance with the License.  You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions
 * and limitations under the License.
 */

package org.apache.storm.starter;

import java.util.Map;
import java.util.Random;

import org.apache.storm.spout.SpoutOutputCollector;
import org.apache.storm.task.OutputCollector;
import org.apache.storm.task.TopologyContext;
import org.apache.storm.topology.ConfigurableTopology;
import org.apache.storm.topology.OutputFieldsDeclarer;
import org.apache.storm.topology.TopologyBuilder;
import org.apache.storm.topology.base.BaseRichBolt;
import org.apache.storm.topology.base.BaseRichSpout;
import org.apache.storm.tuple.Fields;
import org.apache.storm.tuple.Tuple;
import org.apache.storm.tuple.Values;
import org.apache.storm.utils.Utils;

/**
 * This is a basic example of a Storm topology.
 * Reference
 * - https://www.freecodecamp.org/news/apache-storm-is-awesome-this-is-why-you-should-be-using-it-d7c37519a427/
 */
public class ExclamationTopology extends ConfigurableTopology {

    public static void main(String[] args) {
        ConfigurableTopology.start(new ExclamationTopology(), args);
    }

    protected int run(String[] args) {
        TopologyBuilder builder = new TopologyBuilder();

        builder.setSpout("word", new WordSpout(), 1);
        builder.setBolt("exclaim1", new ExclamationBolt(), 1).shuffleGrouping("word");
        builder.setBolt("exclaim2", new ExclamationBolt(), 1).shuffleGrouping("exclaim1");

        conf.setDebug(true);
        conf.setNumWorkers(3);

        String topologyName = "ExclamationTopology";

        if (args != null && args.length > 0) {
            topologyName = args[0];
        }

        return submit(topologyName, conf, builder);
    }

    private static class WordSpout extends BaseRichSpout {

        private SpoutOutputCollector collector;

        @Override
        public void open(Map<String, Object> conf, TopologyContext context, SpoutOutputCollector collector) {
            this.collector = collector;
        }

        @Override
        public void nextTuple() {
            Utils.sleep(1000);
            final String[] words = new String[]{ "kamran", "ali", "sabha", "chotu" };
            final Random rand = new Random();
            final String word = words[rand.nextInt(words.length)];
            collector.emit(new Values(word));
        }

        @Override
        public void declareOutputFields(OutputFieldsDeclarer declarer) {
            declarer.declare(new Fields("word"));

        }
    }

    private static class ExclamationBolt extends BaseRichBolt {
        OutputCollector collector;

        @Override
        public void prepare(Map<String, Object> conf, TopologyContext context, OutputCollector collector) {
            this.collector = collector;
        }

        @Override
        public void execute(Tuple tuple) {
            collector.emit(tuple, new Values(tuple.getString(0) + "!!!")); // Anchoring [To trace origin of tuple]
            collector.ack(tuple); // Tuple being explicitly acknowledged by bolt for being fully processed

            // The ack call will result in the ack method on the spout being called, if it has been implemented.

            // If we’re reading the tuple data from some queue, we can only take it off the queue if the tuple has been fully processed.
            // The ack method is where you’d do that.
        }

        @Override
        public void declareOutputFields(OutputFieldsDeclarer declarer) {
            declarer.declare(new Fields("word"));
        }

    }
}